US4347410AExpiredUtility

Microphone droop and sensitivity measurement device

9
Individually held — no corporate assignee on recordPriority: Feb 26, 1980Filed: Feb 26, 1980Granted: Aug 31, 1982
Est. expiryFeb 26, 2000(expired)· nominal 20-yr term from priority
Inventors:Paul D. SchomerAlan Hunt
H04R 29/004
9
PatentIndex Score
1
Cited by
6
References
72
Claims

Abstract

A device for measuring microphone sensitivity and droop by subjecting the microphone to a negative step function input and recording the microphone electrical response thereto. The microphone is surrounded by an inflated thin, flexible, expandable membrane. The membrane is ruptured resulting in an instantaneous reduction in air pressure on the microphone. It is this instantaneous reduction in air pressure that constitutes the negative step function input to the microphone.

Claims

exact text as granted — not AI-modified
We claim: 
     
       1. An apparatus comprising (a) an acoustical transducer; and   (b) means for subjecting said transducer to a reduction in fluidic pressure at a fast rate such that an acoustic negative step function input is applied to said transducer.   
     
     
       2. The apparatus of claim 1 wherein said reduction in fluidic pressure is instantaneous. 
     
     
       3. The apparatus of claim 1 or 2 wherein said fluidic pressure is reduced from a first specific magnitude to a reference magnitude. 
     
     
       4. The apparatus of claim 1 or 2 wherein said acoustical transducer comprises a condenser microphone. 
     
     
       5. The apparatus of claim 4 wherein said condenser microphone comprises (a) a first movable plate;   (b) a second immovable plate; and   (c) a microphone housing adjacent to said first and second plates defining a cavity between said first and second plates, said housing having an orifice therethrough for venting air from said cavity.   
     
     
       6. The apparatus of claim 5 wherein said fluidic pressure subjecting means comprises, (a) means, enclosing a portion of said housing including said orifice, for expanding when inflated with a fluid;   (b) means for inflating said expandable means with a fluid; and   (c) means for deflating said expandable means thereby effecting said reduction in fluidic pressure.   
     
     
       7. The apparatus of claim 6 wherein said means for deflating includes means for rupturing said expandable means. 
     
     
       8. The apparatus of claim 7 wherein said rupturing means includes non-mechanical means. 
     
     
       9. The apparatus of claim 8 wherein said non-mechanical means includes a source of heat. 
     
     
       10. The apparatus of claim 7 wherein said rupturing means includes mechanical means applied to said expandable means. 
     
     
       11. The apparatus of claim 10 wherein said mechanical means includes an object having a sharp surface. 
     
     
       12. The apparatus of claim 6 wherein said expandable means includes a thin expandable membrane. 
     
     
       13. The apparatus of claim 12 wherein said membrane includes a balloon. 
     
     
       14. The apparatus of claim 6 wherein said means for inflating comprises, (a) an adapter having a passageway for providing fluidic communication from the interior of said expandable means to the exterior of said expandable means; and   (b) a source of fluidic pressure coupled to said adapter passageway.   
     
     
       15. The apparatus of claim 14 wherein said adapter is disposed between said microphone housing and said expandable means. 
     
     
       16. The apparatus of claim 15 wherein said adapter includes, (a) a tube having an inside surface and an outside surface, said microphone housing abutting said inside surface and said expandable means abutting said outside surface; and   (b) means for effecting a fluidic seal between said microphone housing and said inside surface below said venting orifice.   
     
     
       17. The apparatus of claim 16 wherein said fluidic seal means includes an O-ring. 
     
     
       18. The apparatus of claim 14 further comprising a valve coupled between said source of fluidic pressure and said adapter passageway for controlling the fluidic inflation of said expandable means. 
     
     
       19. The apparatus of claim 14 further comprising monitoring means communicating with said passageway for measuring said fluidic pressure within said expandable means. 
     
     
       20. The apparatus of claim 19 wherein said monitoring means includes a manometer. 
     
     
       21. The apparatus of claim 19 further comprising a valve coupled between said measuring means and said passageway for controlling said measuring means. 
     
     
       22. The apparatus of claim 6 wherein said fluidic pressure subjecting means further includes monitoring means for measuring the fluidic pressure within said expandable means. 
     
     
       23. The apparatus of claim 22 wherein said monitoring means includes a manometer. 
     
     
       24. The apparatus of claim 1 or 2 wherein said fluidic pressure subjecting means comprises, (a) means, enclosing said acoustical transducer, for expanding when inflated with a fluid;   (b) means for inflating said expandable means with a fluid; and   (c) means for deflating said expandable means thereby effecting said reduction in fluidic pressure.   
     
     
       25. The apparatus of claim 24 wherein said means for deflating includes means for rupturing said expandable means. 
     
     
       26. The apparatus of claim 25 wherein said rupturing means includes non-mechanical means. 
     
     
       27. The apparatus of claim 26 wherein said non-mechanical means includes a source of heat. 
     
     
       28. The apparatus of claims 24 wherein said rupturing means includes mechanical means applied to said expandable means. 
     
     
       29. The apparatus of claim 28 wherein said mechanical means includes an object having a sharp surface. 
     
     
       30. The apparatus of claim 24 wherein said expandable means includes a thin expandable membrane. 
     
     
       31. The apparatus of claim 30 wherein said membrane includes a balloon. 
     
     
       32. The apparatus of claim 24 wherein said means for inflating comprises, (a) an adapter defining a passageway for providing fluidic communication from the interior of said expandable means to the exterior of said expandable means; and   (b) a source of fluidic pressure coupled to said adapter passageway.   
     
     
       33. The apparatus of claim 32 wherein said adapter is disposed between said transducer and said expandable means. 
     
     
       34. The apparatus of claim 33 wherein said adapter includes, (a) a tube having an inside surface and an outside surface; said transducer abutting said inside surface and said expandable means abutting said outside surface; and   (b) means for effecting a fluidic seal between said transducer and said inside surface.   
     
     
       35. The apparatus of claim 34 wherein said fluidic seal means includes an O-ring. 
     
     
       36. The apparatus of claim 32 further comprising a valve coupled between said source of fluidic pressure and said adapter pasageway for controlling the fluidic inflation of said expandable means. 
     
     
       37. The apparatus of claim 32 further comprising monitoring means communicating with said passageway for measuring said fluidic pressure within said expandable means. 
     
     
       38. The apparatus of claim 37 wherein said monitoring means includes a manometer. 
     
     
       39. The apparatus of claim 37 further comprising a valve coupled between said monitoring means and said passageway for controlling said monitoring means. 
     
     
       40. The apparatus of claim 24 wherein said fluidic pressure subjecting means further includes monitoring means for measuring the fluidic pressure within said expandable means. 
     
     
       41. The apparatus of claim 40 wherein said monitoring means includes a manometer. 
     
     
       42. The apparatus of claim 1 or 2 further including means for measuring and recording the electrical output signal from said transducer. 
     
     
       43. The apparatus of claim 42 wherein said measuring and recording means includes an FM carrier generator and an oscilloscope. 
     
     
       44. The apparatus of claim 1 or 2 wherein said subjecting means further includes monitoring means for measuring said fluidic pressure exerted on said transducer. 
     
     
       45. The apparatus of claim 44 wherein said monitoring means includes a manometer. 
     
     
       46. A method of measuring droop and sensitivity in a condenser microphone comprising the step of subjecting the microphone to an instantaneous reduction in fluidic presure whereby an acoustic negative step function is applied to said microphone. 
     
     
       47. The method of claim 46 wherein the step of subjecting includes the steps of (a) creating an air-tight seal between said microphone and a thin, expandable, flexible membrane;   (b) inflating said membrane to a specific pressure level; and   (c). rupturing said membrane thereby applying an instantaneous reduction in air pressure to said microphone.   
     
     
       48. The method of claim 47 wherein the step of rupturing includes utilizing non-mechanical means for rupturing said membrane. 
     
     
       49. An apparatus comprising (a) an acoustical transducer;   (b) means for applying a positive fluidic pressure with respect to the ambient pressure to said transducer; and   (c) means for reducing said positive fluidic pressure at a fast rate such that an acoustic negative step function is applied to said transducer.   
     
     
       50. The apparatus of claim 49 wherein said positive pressure applying means includes (a) means, enclosing said acoustical transducer, for expanding when inflated with a fluid; and   (b) means for inflating said expandable means with a fluid.   
     
     
       51. The apparatus of claim 50 wherein said pressure reducing means includes means for deflating said expandable means. 
     
     
       52. The apparatus of claim 51 wherein said deflating means includes means for rupturing said expandable means. 
     
     
       53. The apparatus of claim 52 wherein said rupturing means includes non-mechanical means. 
     
     
       54. The apparatus of claim 53 wherein said non-mechanical means include a source of heat. 
     
     
       55. The apparatus of claim 52 wherein said rupturing means includes mechanical means applied to said expandable means. 
     
     
       56. The apparatus of claim 55 wherein said mechanical means includes an object having a sharp surface. 
     
     
       57. The apparatus of claim 50 wherein said expandable means includes a thin expandable membrane. 
     
     
       58. The apparatus of claim 57 wherein said membrane includes a balloon. 
     
     
       59. The apparatus of claim 50 wherein said means for inflating comprises, (a) an adapter defining a passageway for providing fluidic communication from the interior of said expandable means to the exterior of said expandable means; and   (b) a source of fluidic pressure coupled to said adapter passageway.   
     
     
       60. The apparatus of claim 59 wherein said adapter is disposed between said transducer and said expandable means. 
     
     
       61. The apparatus of claim 60 wherein said adapter includes, (a) a tube having an inside surface and an outside surface; said transducer abutting said inside surface and said expandable means abutting said outside surface; and   (b) means for effecting a fluidic seal between said transducer and said inside surface.   
     
     
       62. The apparatus of claim 61 wherein said fluidic seal means includes an O-ring. 
     
     
       63. The apparatus of claim 59 further comprising a valve coupled between said source of fluidic pressure and said adapter passageway for controlling the fluidic inflation of said expandable means. 
     
     
       64. The apparatus of claim 59 further comprising monitoring means communicating with said passage for measuring said fluidic pressure within said expandable means. 
     
     
       65. The apparatus of claim 64 wherein said monitoring means includes a manometer. 
     
     
       66. The apparatus of claim 64 further comprising a valve coupled between said monitoring means and said passageway for controlling said monitoring means. 
     
     
       67. The apparatus of claim 49 wherein said positive fluidic pressure applying means further includes monitoring means for measuring the fluidic pressure within said expandable means. 
     
     
       68. The apparatus of claim 67 wherein said monitoring means includes a manometer. 
     
     
       69. The apparatus of claim 49 further including means for measuring and recording the electrical output signal from said transducer. 
     
     
       70. The apparatus of claim 69 wherein said measuring and recording means includes a FM carrier generator and an oscilloscope. 
     
     
       71. The apparatus of claim 49 wherein said positive fluidic pressure applying means further includes monitoring means for measuring said fluidic pressure exerted on said transducer. 
     
     
       72. The apparatus of claim 71 wherein said monitoring means includes a manometer.

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